[R] query: sample size calculation

ManuelPerera-Chang at fmc-ag.com ManuelPerera-Chang at fmc-ag.com
Fri May 26 14:57:02 CEST 2006

Dear all,

I am doing something wrong.

I am trying to apply a formula for  sample size calculation as in the book
"Design and Analysis of Clinical Trials", from Chow et all.

There a suggested sample size strategy uses the formula


which gives n=96, as in the book.

(here F(alfa,k,n) is the upper (alfa)th quantile of an F distribution with
k,n degrees of freedom)

I have been trying to get n=96 using the following code in R.

 for (n in 1:200) {
  val[n]<- qf(0.8, 2*n, 2*n,lower.tail = TRUE, log.p = FALSE)/qf(0.025,
2*n, 2*n,lower.tail = TRUE, log.p = FALSE);

but val doesnot get any close to 0.30/0.45.

Thank you,


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